Electron discharge device of the magnetron type



9 1950 J. M. sPooNER EIAL 2,493,423

ELECTRON DISCHARGE DEVICE OF THE MAGNETRON TYPE Filed May 29, 1944 28 WW I6 '5 1| '-//VAE7" 2 INVENTOR JOHN M. SPOONER V LLOYD P. GARNER TTORNEY Patented Jan. 3, 1950 ELECTRON DISCHARGE DEVICE OF THE MAGNETRON TYPE John M. Spooner, Manheim Township, Lancaster County, and Lloyd P. Garner, Lancaster, Pa., assignors to Radio; Corporation of America, a.

corporation of Delaware Application May 29, 1944,, Serial No. 537,866.

- Our invention relates to electron discharge devices, particularly to magnetrons in which the electrode system during operation of the device is subjected to a magnetic field.

Magnetrons. dependent upon secondary emission have been recently developed. In this type of tube the main cathode may be of the cold type and coated with secondary emitting material. This cathode may be surrounded by the usual anode arrangement. To initiate emission from the main cathode, a second cathode, of the thermionic type and referred to as a pilot cathode and maintained at or near cathode potential, provides the electrons which are attracted to the main cathode for releasing secondaries. Due to the magnetic field, the path of the primary electrons is such that a considerable portion of them collide with the secondary emission surface of the cold cathode with sufficient velocity to release the secondary electrons. These secondary electrons then traverse a normal cyclic path common to the magnetron structure, a considerable number of which return to the cathode with sufficient energy to. release still more secondary electrons. This process is repeated until an equilibrium condition is reached.

It. is desirable in such types of magnetrons to be able to control the flow of primary electrons in accordance with predetermined conditions and thus the secondary electron current.

An object of our invention is to provide an electron discharge device of the magnetron type in which amplifier action can be produced.

Another object of our invention is to provide an electron discharge device of the magnetron type utilizing secondary emission and in which complete. and desirable control according to predetermined conditions of the primary electrons can. be; assured.

Astill further object of our invention. is toprovideamagnetron of the type described. utilizing grid control and in which grid control is assuredby using secondary cathodes operable at lowtemperatures.

These and other objects will appear hereinafter.

The. novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims, but the invention itself will best beunderstood by reference to the following description taken in connection with the accompanying drawing inwhich Figure I is a longitudinal section of a magnetron made according to our invention, Figure 2 isv a transverse section taken along the line 22 of Claims. (Cl. 250-275)- Figure 1, and Figure 3 taken along the line 33 of Figure 1.

In accordance with our invention we provide a magnetronhaving an anode block Ill of the type now commonly used, which has a plurality of longitudinally extending tubular chambers or bores' H parallel to and spaced around and communicating with a central cathode chamber l I within which a tubular cathode 13 is coaxially positioned with respect to the anode block. The legs I2 formed intermediate the chambers ll act as the anode segments whereas chambers I! act as cavity resonators. An anode lead Ill is provided.

The portion of the cold cathode l3 within the cathode member H" is coated with secondary emitting material #4 and the cathode I3 is provided at one end with a reflector l5 adjacent which is placed a coated thermionic or pilot cathode lfi having leads-ll and it; The reflector i5 and thermionic cathode It are both positionedoutside the cathode chamber. 7

Positioned between the cathode l6 and the oath.- ode coating H3 is a control grid 19 for controlling the emission of primary electrons from the cathode IB. The grid is provided with a lead 20 and is preferably maintained at a lower potential than the cathode l'3 Theanode block I0 is provided with lips 20' and 2| to which are sealed th cup-shaped ends 22 and 23 of insulating material, preferably glass. or ceramic, and through which the ends 24 and 25 of the tubular cathode is are sealed. The purpose of the hollow tubular construction is to permit the flow of cooling fluid through the main cathode. The coil 2% is utilized for providing a magnetic field parallel to the cathode l3 and between the cathode l3 and the anode segments l2.

In order that the grid may maintain control of the cathode emission, it is necessary that there be no primary electrons emitted from it. Cathode material should, therefore, be such that effective secondary emission takes places at low temperatures. This may be done by using silver magnesium material for cathode l3, upon which secondary emitting material is disposed. Since returning secondary electrons bombard cathode l3, a large amount of energy must be removed from it by suitable means. Air cooling may be sufiicient at low duty cycles and water cooling may be necessary if the device is utilized as aoperating the former at a lower potential with the.

grid [9 at a potential lower than that. of either of.

is a transverse section application for which our invention may be employed, it will be apparent that our invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of our invention as set forth in the appended claims.

What we claim as new is:

1. An electron discharge device having an anode provided with a central cathode chamber therein, a first cathode having an electron-emitting surface positioned within said chamber surrounded by the active surface of said anode, a second cathode positioned adjacent but outside of said anode for supplying primary electrons to said chamber, and a control electrode positioned between the emitting surfaces of the second cathode and said first cathode.

2. An electron discharge device having an anode provided with a central cathode chamber therein, a first cathode having an electronemitting surface positioned within said chamber and surrounded by the active surface of said anode, a second cathode positioned adjacent but outside of said anode for supplying primary electrons to said chamber, a control electrode positioned between the emitting surfaces of the second cathode and said first cathode, and means adjacent said electron discharge device for providing a magnetic field between said anode and said first cathode.

3. An electron discharge device having an anode, a hollow cold cathode positioned axially of said anode and coated with secondary emitting material, a thermionic cathode for supplying electrons to the space between said anode and said hollow cathode and positioned outside but adjacent said space, a control electrode positioned between said thermionic cathode and the coated surface of said hollow cathode, and an electron reflectin electrode positioned on said cold cathode on the opposite side of said thermionic cathode from said control electrode, said cold cathode having tubular members extending from the ends of said cold cathode for directing a cooling medium through said cold cathode.

4. An electron discharge device having an anode block provided with a central cathode chamber extending therethrough and a plurality of tubular chambers parallel to said central chamber and opening into said chamber, a hollow cold cathode positioned within the oathode chamber and having a surface coated with secondary emitting material, a thermionic cathode for supplying primary electrons to said cathode chamber and positioned adjacent but outside said cathode chamber, a control electrode between said thermionic cathode and the coated surface of said cold cathode and an electron reflecting electrode positioned on the opposite side of said thermionic cathode from said control electrode, said anode block being provided with sealing lips and cup-shaped insulating members sealed to said lips and providing with said anode block an envelope for said cathodes, control electrode and reflecting electrode, said 4 hollow cold cathode having tubular members communicating with the interior thereof and extending through said envelope.

5. An electron discharge device having an anode block provided with a central cathode chamber extending therethrough and a plurality of tubular chambers parallel to said central chamber and opening into said chamber, a cold cathode positioned within the cathode chamber and having a surface coated with secondary emitting material, a thermionic cathode adjacent but outside said cathode chamber for supplying primary electrons to said cathode chamher, a control electrode between said thermionic cold cathode and the coated surface of said cathode, and an electron reflecting electrode positioned on the opposite side of said thermionic cathode from said control electrode, said anode block bein provided with sealing lips and cupshaped insulating members sealed to said anode block and providing with said anode block an envelope for said cathodes, control electrode and reflecting electrode.

6. An electron discharge device having an anode block provided with a central cathode chamber extending therethrough and a plurality of tubular chambers parallel to said central chamber and opening into said central chamber, a hollow cold cathode positioned within the cathode chamber and having a surface coated with emitting material, a thermionic cathode adjacent but outside the cathode chamber for supplying primary electrons to said cathode chamber, and a control electrode for said thermionic cathode positioned between said thermionic cathode and the coated surface of said cold cathode, said hollow cold cathode havin tubular members opening into the interior thereof and extending from the ends of said cold cathode.

7. An electron discharge device having an anode block provided with a central cathode chamber extending therethrough and a plurality of tubular chambers parallel to said central chamber and opening into said central chamber, a hollow cold cathode positioned within the cathode chamber and having a surface coated with secondary emitting material, a thermionic cathode adjacent but outside said cathode chamber for supplying primary electrons to said cathode chamber, a control electrode for said thermionic cathode positioned on one side of said thermionic cathode, a reflecting electrode positioned on the opposite side of said thermionic cathode from said control electrode, said hollow cold cathode having tubular members opening into the interior thereof and extending from the ends of the cold cathode, and means adjacent bers extending from the ends of said cold cathode for directing a cooling medium through said cold cathode.

9. An electron discharge device having an anode, a tubular cold cathode positioned axially of said anode and coated with secondary emitting material on its outer surface, a thermionic cathode for supplying electrons to the space between said anode and said tubular cathode adjacent but outside said space, a control electrode positioned between said thermionic cathode and the coated surface of said tubular cathode, and. a reflecting electrode positioned on said cold cathode on the opposite side of said thermionic cathode from said control electrode.

10. An electron discharge device according to claim 1, wherein said first cathode is tubular and is provided with tubular members extending from the ends thereof for directing a cooling medium therethrough.

JOHN M. SPOONER. LLOYD P. GARNER.

REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date Re. 22,724 Varian et al. Feb. 19, 1946 1,757,233 Bol May 6, 1930 10 1,970,532 Bouwers Aug. 14, 1934 2,009,369 Hansell July 23, 1935 2,163,157 Samuel June 20, 1939 2,400,770 Mouromtsefi et al. May 21, 1946 2,409,038 Hansell Oct. 8, 1946 15 2,450,763 McNall Oct. 5, 1948 FOREIGN PATENTS Number Country Date 509,102 Great Britain July 11, 1939 20 Certificate of Correction Patent No. 2,493,423 January 3, 1950 JOHN M. SPOONER ET AL.

It is herebycertified that error appears in the printed specification of the above nurh'b'e red patent requiring correction as follows:

Column 2, line 11, strike out the Word the, second occurrence; line 12, before chambers insert the; line 13, for lead 10 read lead 10; column 4, line 15, strike out cold and insert the same before cathode, in line 16, same column;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office. Signed and sealed th1s 3rd day of October, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commz'ssioner of Patents. 

